Abstract: 【Objective】 The experiment was conducted to study the mutagenic effects of space environment on seedling growth in M1, plant height and heading date in M2 in rice. 【Method】 Two types of lines of growth promotion (GP) and growth suppression (GS) were selected from the recombinant inbred lines derived from a cross between a sensitive japonica Lemont and a nonsensitive indica Teqing to compare mutation frequency and mutagenic efficiency for plant height and heading date in M2 generation. 【Result】Space environment resulted in 34.9% higher seedling height in GP group than in the control and 39.1% lower in GS group than in the control, and there was no difference in seed fertility between the two groups. In M2, mutants of plant height and heading date can be induced by space treatment in both the two groups with lower mutation frequency and mutagenic efficiency in GP group than in GS group. There were no significant differences in physiological damages in M1 between the two groups after γ-rays irradiation treatment. Mutation frequency and mutagenic efficiency of heading date in M2 were higher in GS group than in GP group, and opposite was true for mutagenic efficiency of plant height although the mutation frequency varied between the two groups. The mutation frequencies of plant height and heading date induced by space environment were obviously lower than those by γ-rays irradiation, but the mutagenic efficiency was opposite for the most traits. 【Conclusion】 For GP and GS of seedlings induced by space environment, GS had higher mutation frequency and mutagenic efficiency of plant height and heading date than GP in M2.

Key words: Rice, Sapce environment mutation, Mutagenic effect, Physiological damage, Mutation breeding